Methods and structures for increasing the allowable die size in tmv packages

ABSTRACT

A package includes a substrate having an electronic component flip chip mounted thereto by flip chip bumps. The electronic component includes an active surface and an inactive surface. Electrically conductive columns (TSV) extend through the electronic component between the active surface and the inactive surface. A RDL structure is coupled to the inactive surface, the RDL structure redistributing the pattern of the electrically conductive columns at the inactive surface to a pattern of inactive surface RDL lands. The inactive surface RDL lands are exposed through via apertures of a package body. By using the inactive surface of the electronic component to distribute the inactive surface RDL lands, the allowable size of the electronic component is maximized.

RELATED APPLICATION

The present application claims benefit of Nicholls et al, U.S. Provisional Application No. 61/444,306, entitled “METHODS AND STRUCTURES FOR INCREASING THE ALLOWABLE DIE SIZE IN TMV PACKAGES”, filed on Feb. 18, 2011, which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present application relates to the field of electronics, and more particularly, to methods of forming electronic component packages and related structures.

BACKGROUND

The current trend is to integrate vertically by stacking packages (3D Packaging). There are several packaging formats currently being used to accomplish this: (1) Traditional Package-on-Package (PoP) with bare die or pin gate molding; (2) Package-in-Package (PiP); and (3) Thru-Mold Via (TMV).

In each of these formats, the space needed to accommodate the vertical structures limits the space available on the bottom package for the main logic die. The challenge is to maximize the die size allowed in the bottom package while maintaining the same package-to-package I/O currently used.

Until now, the main focus has been to reduce the BGA pitch of the top package so that more I/O can fit on one or two perimeter rows which then gives more space in the middle for the die in the bottom package. One challenge to this approach is with tighter pitches on the top package, the top package BGA ball becomes smaller which affects both stand-off, and collapse.

In TMV format, there is the added challenge of “building up” the solder within the TMV package to achieve a relatively tall bump with a tight pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate an embodiment using narrow pillars in the TMV (Thru-Mold Via);

FIG. 3 illustrates another embodiment using narrow pillars in the TMV;

FIGS. 4 and 5 illustrate an embodiment using wire bonds to route up to BGA (Ball Grid Array) locations;

FIGS. 6, 7, and 8 illustrate an embodiment using wire bond loops as vertical connection;

FIG. 9 illustrates an embodiment using laser ablation;

FIGS. 10 and 11 illustrate an embodiment using routing around the edge of the package;

FIGS. 12, 13, and 14 illustrate an embodiment using a TSV (Thru-Silicon Via) version of TMV;

FIGS. 15, 16, 17 and 18 illustrate an embodiment using a ball pad opening through the solder mask by laser;

FIGS. 19, 20, 21 illustrate an embodiment using a ball pad opening covered with a film;

FIGS. 22, 23, 24, 25, 26, and 27 illustrate an embodiment using redistribution using an interposer or RDL structure;

FIG. 28 illustrates an embodiment using a wire bonded interposer with a TMV connection; and

FIG. 29 illustrates an embodiment using specially shaped pads to increase the distance between the die edge and the TMV pads.

In the following description, the same or similar elements are labeled with the same or similar reference numbers.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate an embodiment using narrow pillars in the TMV (Thru-Mold Via). More particularly, FIG. 1 illustrates a narrow pillar 102 formed from a single long copper stud bond formed, for example, using a wire bonding apparatus. FIG. 2 illustrates a narrow pillar 202 formed from multiple copper stud bonds 204 one on top of another formed, for example, using a wire bonding apparatus.

Although two copper stud bonds 204 are illustrated as forming narrow pillar 202 in FIG. 2, in other embodiments, more than two, e.g., three, four, or more, copper stud bonds 204 are used to form a narrow pillar 202.

By using a single, long copper stud bond (narrow pillar 102), or a multiple copper stud bond (narrow pillar 202), the diameter of the bond can be reduced, for example, from 250 μm diameter to approximately 100 um diameter which would give an immediate increase of 150 um for die size.

Additionally, if the copper stud bond is done at, for example, 200° C. or below, the copper stud bonds can be formed before flip chip attach. This would allow for more flexibility for capillary underfill (CUF) bleed increasing the allowable die size.

The copper wire used to form narrow pillars 102, 202 could be pure copper or coated copper wire with a coating such as Palladium or other suitable coating.

Narrow pillars 102, 202 are formed, for example, on solder mask defined (SMD) pads of substrates 106, 206, respectively. Narrow pillars 102, 202 including the electronic components mounted to substrates 106, 206 are then enclosed within a molding compound similar to the package as shown in FIG. 3.

In one embodiment, the molding compound is laser ablated to expose narrow pillars 102, 202. As narrow pillars 102, 202, and in particular narrow pillars 202, are relatively tall, the amount of molding compound that must be removed to expose narrow pillars 102, 202 is minimized. This allows the via apertures, sometimes called TMV, formed during the laser ablation to be relatively short, i.e., to have a shallow depth, and thus to have a minimum diameter.

FIG. 3 illustrates another embodiment using narrow pillars in the TMV. More particularly, FIG. 3 illustrates a substrate 306 having interconnection balls 308, e.g., a ball grid array (BGA), on a lower surface of substrate 306. An electronic component 310, e.g., an integrated circuit die, is flip chip mounted to an upper surface of substrate 306 using flip chip bumps 312.

Similar to the embodiment discussed above regarding FIGS. 1 and 2, narrow pillars 302 are formed but using a longer wire with ball bond 303 on the substrate pad, and longer “tail” wire 304 extending most of the way, or all of the way to the top of the package 300 from ball bond 303.

With this method, it is suitable to use a relatively thick copper wire, e.g., 6 mils, and then provide a copper ball bond 303 on the substrate pad, then extend the tail of the bond straight up to the top of the package, and using the spark to assist in breaking the wire at the correct location to give the long tail wire 304.

In this embodiment, the copper wire can consist of essentially pure copper, or a coated copper wire with a suitable coating such as Palladium.

More particularly, after flip chip mounting of electronic component 310 and formation of narrow pillars 302, electronic component 310, narrow pillars 302 and the exposed upper surface of substrate 306 are enclosed within a dielectric package body 314, e.g., molding compound. Tail wires 304 of narrow pillars 302 are exposed at a principal, or top, surface 316 of package body 314.

Package 300 can be utilized with other packages and/or interposers, e.g., in a stacked arrangement.

FIGS. 4 and 5 illustrate an embodiment using wire bonds to route up to BGA (Ball Grid Array) locations. The substrate bond pads 408 of a substrate 406 are moved out to the perimeter of the package 400, and then “routed” in 3D by using formed wire bonding 410, i.e., wires, to BGA locations 412, thus allowing to greatly increase the allowable die size in the TMV package 400.

By using wire bonding technology to route to a space above the die, the die cavity size is effectively increased, for example, by a minimum of 0.8 mm in both X and Y directions.

The wire used could be a gold wire, a copper wire, or a coated copper wire with a suitable coating such as Palladium.

Formed wire bonding 410, sometimes called a narrow pillar, including the electronic component mounted to substrate 406 are then enclosed within a molding compound similar to the package as shown in FIG. 3.

FIGS. 6, 7, and 8 illustrate an embodiment using wire bonds loops as vertical connection. An alternative method of a wire loop pad 602 includes making the loop 604 on lead fingers 606. The wire used can be gold, copper, or a coated copper wire with a suitable coating such as Palladium. Loop 604 is sometimes called a narrow pillar.

FIG. 9 illustrates an embodiment using laser ablation. For the above embodiments, e.g., those shown in FIGS. 1-8, a laser may be used to ablate the epoxy mold compound, e.g., package body 314, to form via apertures 918 in order to expose the top portion of the wire or conductor 902, e.g., a narrow pillar as described above. This allows for an upper package to be aligned and soldered to the lower package 900 by aligning the solder pads of the upper package with the exposed conductors 902 of the lower package 900 and performing a solder reflow operation.

Although conductors 902 are illustrated in FIG. 9 as being exposed through laser ablated via apertures 918, in other embodiments, narrow pillars 102, 202, 302 of FIGS. 1-3, formed wire bonding 410 of FIGS. 4-5, and/or loops 604 of FIGS. 6-8 are exposed through via apertures 918 in a similar manner.

FIGS. 10 and 11 illustrate an embodiment using routing around the edge of the package. By routing around the edge 1002 and along the top 1004 of the package 1000 to the top package BGA location 1006, the allowable die size has a maximum increase.

This embodiment utilizes laser ablation or mechanical drilling and metallization techniques to form the interconnect from a pad on the substrate, along the edge 1002 of the package 1000, and along the top 1004 of the package 1000 to the BGA location 1006.

More particularly, laser ablated or drilled vias 1008 are formed in a saw street 1010 such that the edges of the vias 1008 extend slightly into the edge 1002 of the package 1000. Vias 1008 are filled with an electrically conductive material to form conductors along the edge 1002 of package 1000. Further, conductors are formed along the top 1004 of package 1000, and these conductors are connected to the conductors along the edge 1002 of package 1000. The array of packages 1000 is then singulated along saw streets 1010 to provide discrete routing (conductors) along the edge 1002 and top 1004 of package 1000.

FIGS. 12, 13, and 14 illustrate an embodiment using a TSV (Thru-Silicon Via) version of TMV. The embodiment includes TSV on the bottom die, RDL (ReDistribution Layer) for the die backside metallization, and laser ablating through the mold to expose the RDL pads on the backside of the die.

More particularly, paying particular attention to FIG. 12, electronic component 310 includes an active surface 1202 and an opposite inactive surface 1204. Active surface 1202 includes the active circuitry of electronic component 310 and also includes bond pads, sometime called the Input/Output (I/O) pads of electronic component 310.

Thru-Silicon Vias (TSVs) 1206, e.g., electrically conductive columns, extend through electronic component 310 between active surface 1202 and inactive surface 1204. TSVs 1206 and the bond pads at active surface 1202 are electrically and physically connected to substrate 306 by flip chip bumps 312, e.g., solder bumps.

In one embodiment, a ReDistribution Layer (RDL) structure 1208 is formed on inactive surface 1204 of electronic component 310. RDL structure 1208 includes a dielectric passivation layer 1210 on inactive surface 1204 that is patterned to expose TSVs 1206 at inactive surface 1204. RDL structure 1208 further includes an electrically conductive circuit pattern 1212, sometimes called an RDL, formed on passivation layer 1210 and electrically connected to TSVs 1206 through the openings in passivation layer 1210. Illustratively, circuit pattern 1212 is formed by plating and etching an electrically conductive material such as copper although is formed using other techniques in other embodiments.

Circuit pattern 1212 redistributes the pattern of TSVs 1206 at inactive surface 1204 to the pattern of inactive surface RDL lands 1214 of circuit pattern 1212. Although a single passivation layer 1210 and circuit pattern 1212 are discussed above and illustrated, in other embodiments, RDL structure 1208 includes multiple dielectric layers and/or multiple circuit patterns that redistributes the pattern of TSVs 1206 at inactive surface 1204 to the pattern of inactive surface RDL lands 1214.

Referring now to FIG. 13, electronic component 310 including RDL structure 1208 and the exposed portion of the upper surface of substrate 306 are enclosed in a dielectric package body 1316, e.g., molding compound.

Referring now to FIG. 14, via apertures 1418, sometimes called TMV, are formed in package body 1316 to expose inactive surface RDL lands 1214. By using inactive surface 1204 to distribute inactive surface RDL lands 1214, the allowable size of electronic component 310 is maximized.

FIGS. 15, 16, 17 and 18 illustrate an embodiment using a ball pad opening through the solder mask by a laser. In accordance with this embodiment, the solder mask is left over the bond pads to act as an UF (Under Fill) dam and ball pad openings are formed by laser.

More particularly, referring to FIG. 15, an opening 1502 is formed in a solder mask 1504 on or part of the upper surface of substrate 306. Electronic component 310 is flip chip mounted to substrate 306 in opening 1502, e.g., with flip chip bumps 312. Pads 1514 of substrate 306 remain covered and protected by solder mask 1504, sometimes called a pad protectant layer. Pads 1514 are outward of electronic component 310.

Referring now to FIG. 16, a dielectric underfill 1616 is applied between electronic component 310 and substrate 306 and around flip chip bumps 312. In one embodiment, underfill 1616 bleeds out above pads 1514. However, pads 1514 are covered and protected by solder mask 1504. As there is no risk of resin bleed out (RBO), i.e., there is no risk of contamination of pads 1514 (sometimes called ball pads) by underfill 1616, the die size is maximized.

Referring now to FIG. 17, solder mask 1504 is laser ablated to form solder mask openings 1718 therein. Solder mask openings 1718 expose pads 1514 for electric connection thereto by other structures.

Referring now to FIG. 18, in another embodiment, a solder mask opening 1820 is formed in solder mask 1504 to expose traces 1822 on or embedded within the upper surface of substrate 306. The exposed traces 1822 are electrically connected together with wires 1824, for example, to provide a pad to pad bond.

FIGS. 19, 20, 21 illustrate an embodiment using a ball pad opening covered with a film. More particularly, referring to FIG. 19, pads 1514 are covered and protected by a removable film 1902, e.g., a UV film. Removable film 1902 has a removable film opening 1904 therein. Removable film 1902 is sometimes called a pad protectant layer.

Electronic component 310 is flip chip mounted to substrate 306, e.g., with flip chip bumps 312, and within removable film opening 1904. Pads 1514 of substrate 306 remain covered and protected by removable film 1902.

Referring now to FIG. 20, a dielectric underfill 2016 is applied between electronic component 310 and substrate 306 and around flip chip bumps 312. In one embodiment, underfill 2016 bleeds out above pads 1514. However, pads 1514 are covered and protected by removable film 1902. As there is no risk of resin bleed out (RBO), i.e., there is no risk of contamination of pads 1514 (sometimes called ball pads) by underfill 2016, the die size is maximized. In one embodiment, underfill 2016 is cured after application.

Referring now to FIG. 21, removable film 1902 is removed, sometimes called stripped, to expose pads 1514 for electric connection thereto by other structures.

As set forth above, the ball pad opening that exposes pad 1514 is covered by removable film 1902. Further, removable film 1902 is peeled off after cure of underfill 2016. There is no risk of RBO, the die size is maximized, and there is no risk of contamination on the ball pad 1514.

FIGS. 22, 23, 24, 25, 26, and 27 illustrate an embodiment using redistribution using an interposer or RDL structure. In accordance with one embodiment, a stud or post is applied for the vertical connection. After molding, a grind down is performed to expose the post. An interposer or RDL structure is applied which fans I/O (Input/Output) from the perimeter.

More particularly, referring to FIG. 22, electronic component 310 is flip chip mounted to the upper surface of substrate 306 with flip chip bumps 312.

Referring now to FIG. 23, metallic studs 2314, sometimes called posts, are formed, for example, by plating, on pads 2316 on the upper surface of substrate 306. Pads 2316 are outward of electronic component 310, i.e., electronic component 310 is inward of pads 2316.

As shown in FIG. 24, electronic component 310, studs 2314, and the exposed upper surface of substrate 306 are enclosed in a dielectric package body 2418, e.g., molding compound. Package body 2418 and, optionally, inactive surface 1204 of electronic component 310, are then ground down from a principal surface 2420 of package body 2418 to expose studs 2314 as illustrated in FIG. 25. Although studs 2314 are illustrated as protruding above principal surface 2420 in FIG. 25, in another embodiment, studs 2314 are flush with principal surface 2420.

As illustrated in FIG. 26, an interposer 2622, e.g., a silicon, laminate, or other type of discrete interposer, is mounted to principal surface 2420 of package body 2418 and to inactive surface 1204 of electronic component 310. Interposer 2622 is electrically coupled to exposed studs 2314.

Interposer 2622 redistributes the pattern of studs 2314 to a pattern of outer interposer pads 2624. As illustrated, at least some of outer interposer pads 2624 are located directly above electronic component 310. By fanning in the pattern of studs 2314 above the area of electronic component 310, the allowable size of electronic component 310 is maximized.

FIG. 27 illustrates another embodiment of the package of FIG. 25 at a later stage during fabrication and including a RDL structure 2726. In one embodiment, RDL structure 2726 is formed on inactive surface 1204 of electronic component 310 and principal surface 2420 of package body 2418. RDL structure 2726 includes a dielectric passivation layer 2728 on inactive surface 1204 and principal surface 2420 that is patterned to expose studs 2314.

RDL structure 2726 further includes an electrically conductive circuit pattern 2730, sometimes called an RDL, formed on passivation layer 2728 and electrically connected to studs 2314. Illustratively, circuit pattern 2730 is formed by plating and etching an electrically conductive material such as copper although is formed using other techniques in other embodiments.

Circuit pattern 2730 redistributes the pattern of studs 2314 to the pattern of inactive surface RDL lands 2732 of circuit pattern 2730. Although a single passivation layer 2728 and circuit pattern 2730 are discussed above and illustrated, in other embodiments, RDL structure 2726 includes multiple dielectric layers and/or multiple circuit patterns that redistribute the pattern of studs 2314 to the pattern of inactive surface RDL lands 2732.

As illustrated, at least some of inactive surface RDL lands 2732 are located directly above electronic component 310. By fanning in the pattern of studs 2314 above the area of electronic component 310, the allowable size of electronic component 310 is maximized.

FIG. 28 illustrates an embodiment using a wire bonded interposer with a TMV connection. In accordance with this embodiment, an interposer is applied to the backside of the die, connections are wire bonded to the interposer, and openings are laser ablated to expose the interposer pads.

More particularly, electronic component 310 is flip chip mounted to substrate 306 with flip chip bumps 312. An interposer 2814, e.g., a silicon, laminate, or other type of discrete interposer, is mounted, e.g., with solder, adhesive, or otherwise bonded, to inactive surface 1204 of electronic component 310. Interposer lands 2816 of interposer 2814, e.g., around the outer periphery of interposer 2814, are electrically coupled to pads 2316 of substrate 306 with electrically conductive bond wires 2818.

Interposer 2814 and bond wires 2818 redistributes the pattern of pads 2316 of substrate 306 to a pattern of outer interposer pads 2820 of interposer 2814. As illustrated, outer interposer pads 2820 are located directly above electronic component 310.

Electronic component 310, interposer 2814, bond wires 2818, and the exposed portion of the upper surface of substrate 306 are enclosed in a dielectric package body 2822, e.g., molding compound.

Via apertures 2824, sometimes called TMV, are formed in package body 2822 to expose outer interposer pads 2820. By forming outer interposer pads 2820 above inactive surface 1204, the allowable size of electronic component 310 is maximized.

Referring now to FIGS. 14 and 28 together, in another embodiment, interposer 2814 of FIG. 28 is used to redistribute the pattern of TSVs 1206 (FIG. 14) to the pattern of outer interposer pads 2820 (FIG. 28). Stated another way, the package as illustrated in FIG. 14 is formed with interposer 2814 of FIG. 28 instead of RDL structure 1208 of FIG. 14.

In yet another embodiment, referring still to FIGS. 14 and 28 together, RDL structure 1208 of FIG. 14 and bond wires 2818 (FIG. 28) are used to redistribute the pattern of pads 2316 of substrate 306 (FIG. 28) to the pattern of inactive surface RDL lands 1214 (FIG. 14). Stated another way, the package as illustrated in FIG. 28 is formed with RDL structure 1208 of FIG. 14 instead of interposer 2814 of FIG. 28.

FIG. 29 illustrates an embodiment using specially shaped pads to increase the distance between the die edge and the TMV pads. In accordance with this embodiment, a special shaped TMV pad 2902 is applied to maximize the distance from the die edge to the TMV pad without adversely affecting the location of the TMV ball. A “D” shaped pad 2902 is an example of one embodiment. In one embodiment, all of the pads of substrate 306 are D shaped pads 2902, for example, to provide consistent height of solder reflowed on the pads of substrate 306.

Further, although D shaped pads 2902 are illustrated, in other embodiments, pads 2902 have other shapes, e.g., C shape.

The various packages as described herein are used in a variety of applications. For example, the packages can be stacked, e.g., can be a lower package with another package or structure stacked on top or can be the upper package stacked upon a lower package or structure. Further, additional interposers can be mounted to the packages or the packages can be mounted to interposers. Although specific applications are discussed here, in light of this disclosure, those of skill in the art will understand that the packages can be used in other applications.

Although specific embodiments were described herein, the scope of the invention is not limited to those specific embodiments. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is at least as broad as given by the following claims. 

1-31. (canceled)
 32. An electronic package comprising: a substrate comprising an upper substrate side; an electronic component comprising an upper component side, a lower component side, and lateral component sides, the lower component side coupled to the upper substrate side; a first plurality of wires laterally displaced from a first lateral component side of the electronic component, each of the first plurality of wires comprising a first upper wire end and a first lower wire end, the first lower wire end of each of the first plurality of wires coupled to the upper substrate side; and a package body enclosing the first plurality of wires and the electronic component, the package body comprising a lower package body side facing the substrate and an upper package body side facing away from the substrate, the first upper wire end of each of the first plurality of wires exposed from the upper package body side of the package body.
 33. The electronic package of claim 32, wherein the first plurality of wires is arranged in a row at the first lateral component side.
 34. The electronic package of claim 33, wherein the row of the first plurality of wires is parallel to the first lateral component side.
 35. The electronic package of claim 32, further comprising a second plurality of wires laterally displaced from a second lateral component side of the electronic component, each of the second plurality of wires comprising a second upper wire end and a second lower wire end, the second lower wire end of each of the second plurality of wires coupled to the upper substrate side, and the second upper wire end of each of the second plurality of wires exposed from the upper package body side of the package body.
 36. The electronic package of claim 32, wherein the first upper wire end of each of the first plurality of wires is coplanar with the upper package body side.
 37. The electronic package of claim 32, further comprising an upper conductor coupled to the first upper wire end of each of the first plurality of wires.
 38. The electronic package of claim 32, wherein the substrate comprises a trace at the upper substrate side, the first lower wire end of each of the first plurality of wires coupled to the trace.
 39. The electronic package of claim 38, wherein the trace is exposed from a solder mask opening formed in a solder mask.
 40. The electronic package of claim 32, wherein at least a portion of each of the first plurality of wires is coated with a metal.
 41. The electronic package of claim 32, comprising an upper conductive layer coupled to the first upper wire end of each of the first plurality of wires.
 42. An electronic package comprising: a substrate comprising an upper substrate side; an electronic component comprising an upper component side, a lower component side, and lateral component sides, the lower component side coupled to the upper substrate side; a first row of wires laterally displaced from a first lateral component side of the electronic component, each of the first row of wires comprising a first upper wire end and a first lower wire end, the first lower wire end of each of the first row of wires coupled to the upper substrate side; a second row of wires laterally displaced from a second lateral component side of the electronic component, each of the second row of wires comprising a second upper wire end and a second lower wire end, the second lower wire end of each of the second row of wires coupled to the upper substrate side; and a package body enclosing the first row of wires, the second row of wires, and the electronic component, the package body comprising a bottom package body side facing the substrate and top package body side facing away from the substrate, the first upper wire end of each of the first row of wires and the second upper wire end of each of the second row of wires exposed from the top package body side of the package body.
 43. The electronic package of claim 42, wherein the first row of wires is parallel to the first lateral component side.
 44. The electronic package of claim 42, wherein the second row of wires is parallel to the second lateral component side.
 45. The electronic package of claim 42, wherein the first upper wire end of each of the first row of wires is coplanar with the second upper wire end of each of the second row of wires.
 46. The electronic package of claim 42, wherein each of the first row of wires and the second row of wires comprises copper wires.
 47. The electronic package of claim 42, further comprising an upper conductive layer coupled to the first upper wire end of each of the first row of wires and to the second upper wire end of each of the second row of wires.
 48. The electronic package of claim 47, wherein at least a portion of the upper conductive layer is positioned directly above the electronic component.
 49. A method of making an electronic package, the method comprising: providing a substrate comprising an upper substrate side; providing an electronic component comprising an upper component side and a lower component side, and lateral component sides, the lower component side coupled to the upper substrate side; providing a plurality of wires laterally displaced from a lateral component side of the electronic component, each of the plurality of wires comprising an upper wire end and a lower wire end, the lower wire end of each of the plurality of wires coupled to the upper substrate side; and forming a package body enclosing the plurality of wires and the electronic component, the package body comprising a lower package body side facing the substrate and an upper package body side facing away from the substrate, the upper wire end of each of the plurality of wires exposed from the upper package body side of the package body.
 50. The method of claim 49, further comprising forming a solder mask opening in a solder mask to expose a trace at the upper substrate side, the lower wire end of each of the plurality of wires coupled to the trace.
 51. The method of claim 49, further comprising forming an upper conductive layer coupled to the upper wire end of each of the plurality of wires. 